xargs

Execute utility, passing constructed argument list(s).
Read space, tab, newline and end-of-file delimited arguments from standard input
and execute the specified utility with them as arguments. The arguments
are typically a long list of filenames (generated by ls or find, for example)
that get passed to xargs via a pipe.

Syntax
xargs [-0pt] [-E eofstr] [-I replstr [-R replacements]] [-J replstr]
[-L number] [-n number [-x]] [-P maxprocs] [-s size]
[utility [argument ...]]
If no utility is specified, echo is used.
Key
-0
Change xargs to expect NUL (`\0') characters as separators,
instead of spaces and newlines. This is expected to be used in
concert with the -print0 function in find.
-E eofstr
Use eofstr as a logical EOF marker.
-I replstr
Execute utility for each input line, replacing one or more
occurences of replstr in up to replacements (or 5 if no -R flag
is specified) arguments to utility with the entire line of input.
The resulting arguments, after replacement is done, will not be
allowed to grow beyond 255 bytes; this is implemented by concate-
nating as much of the argument containing replstr as possible, to
the constructed arguments to utility, up to 255 bytes. The 255
byte limit does not apply to arguments to utility which do not
contain replstr, and furthermore, no replacement will be done on
utility itself. Implies -x.
-J replstr
If this option is specified, xargs will use the data read from
standard input to replace the first occurrence of replstr instead
of appending that data after all other arguments. This option
will not effect how many arguments will be read from input (-n),
or the size of the command(s) xargs will generate (-s). The
option just moves where those arguments will be placed in the
command(s) that are executed. The replstr must show up as a dis-
tinct argument to xargs. It will not be recognized if, for
instance, it is in the middle of a quoted string. Furthermore,
only the first occurrence of the replstr will be replaced. For
example, the following command will copy the list of files and
directories which start with an uppercase letter in the current
directory to destdir:
/bin/ls -1d [A-Z]* | xargs -J % cp -rp % destdir
-L number
Call utility for every number lines read. If EOF is reached and
fewer lines have been read than number then utility will be
called with the available lines.
-n number
Set the maximum number of arguments taken from standard input for
each invocation of the utility. An invocation of utility will
use less than number standard input arguments if the number of
bytes accumulated (see the -s option) exceeds the specified size
or there are fewer than number arguments remaining for the last
invocation of utility. The current default value for number is
5000.
-o
Reopen stdin as /dev/tty in the child process before executing the command.
This is useful if you want xargs to run an interactive application.
-P maxprocs
Parallel mode: run at most maxprocs invocations of utility at once.
-p
Echo each command to be executed and ask the user whether it should be executed.
An affirmative response, `y' in the POSIX locale, causes the command to be executed,
any other response causes it to be skipped. No commands are executed if the
process is not attached to a terminal
-R replacements
Specify the maximum number of arguments that -I will do replacement in.
-s size
Set the maximum number of bytes for the command line length pro-
vided to utility. The sum of the length of the utility name, the
arguments passed to utility (including NULL terminators) and the
current environment will be less than or equal to this number.
The current default value for size is ARG_MAX - 4096.
-t
Echo the command to be executed to standard error immediately before it is executed.
-x
Force xargs to terminate immediately if a command line containing
number arguments will not fit in the specified (or default) command
line length.

The utility and any arguments specified on the command line are given to
the utility upon each invocation, followed by some number of the arguments
read from standard input. The utility is repeatedly executed until standard
input is exhausted.

Spaces, tabs and newlines may be embedded in arguments using single
( ' ) or double ( " ) quotes or backslashes ( \ ). Single quotes escape all
non-single quote characters, excluding newlines, up to the matching single quote.
Double quotes escape all non-double quote characters, excluding newlines, up
to the matching double quote. Any single character, including newlines, may
be escaped by a backslash.

Undefined behavior may occur if utility reads from the
standard input.

The xargs utility exits immediately (without processing any further
input) if a command line cannot be assembled, utility cannot be invoked, an
invocation of the utility is terminated by a signal or an invocation of the
utility exits with a value of 255.

xargs exits with a value of 0 if no error occurs.
If utility cannot be found, xargs exits with a value of 127, otherwise
if utility cannot be executed, xargs exits with a value of 126. If any
other error occurs, xargs exits with a value of 1.

Examples

Touch all the files in the current directory (.) to be dated 31st December (12 31) at 09.30, -print0 is required if any filenames contain whitespace.